The present invention relates to passenger conveyor.
Such passenger conveyors are e.g. escalators or moving walkways. Escalators are passenger conveyors that typically carry passengers between landings at different levels. Moving walkways are usually used to carry passengers along levels extending horizontally or with only slight inclination.
Such passenger conveyor typically includes a frame, balustrades with movable handrails, an endless transportation band or tread band (e.g. a step band or pallet band), a drive system and a transportation chain or drive chain for propelling the tread band. The drive chain travels in an endless way between sheaves or sprockets located at an upstream landing and a downstream landing, respectively. The drive chain comprises a plurality of drive chain links, each of the drive chain links having associated thereto a respective drive chain roller, consecutive of the drive chain links being connected via a respective of the drive chain rollers. The drive chain is guided by a drive chain guide fixed to the frame. The drive chain guide may e.g. interact with the drive chain rollers. The frame includes a truss section on both left and right hand sides of the frame. Each truss section has two end sections forming landings, connected by an inclined or—in case of a moving walkway—a horizontal midsection. Frequently, one of the landings houses the drive system or machine of the passenger conveyor positioned between the trusses.
The present invention particularly pertains to a passenger conveyor with an endless tread band that is composed of several transportation elements or treads (e.g. in the form of steps or pallets). A tread includes a tread surface defined by a front side, a rear side and two lateral sides, and is connected to at least one drive chain (usually termed step chain or pallet chain), e.g. via a drive chain axle and drive chain rollers. In many cases there are provided two lateral transport chains running in parallel along endless paths.
In case of a moving walkway travelling between an upstream landing and a downstream landing without significant inclination, it may be more appropriate to say that the drive chain is driven around an upstream and a downstream turnaround section. In case of an escalator the turnaround sections commonly are designated as lower and upper turnaround sections.
The drive system of a passenger conveyor typically comprises the drive chain, a drive chain drive wheel (e.g. in the form of a sprocket or toothed wheel), an axle and a drive motor. The drive chain travels a continuous, closed loop, running from one landing to the other landing, and back. The drive chain is drivably connected to the treads, e.g. via supporting respective of the treads pivotably by drive chain roller axles which support drive chain rollers of the drive chain. The drive motor drives, directly or via a further transmission, the drive sheave which is in a driving connection with the drive chain. Commonly the final drive is realized as one or a pair of chain turnaround drive wheels located in a turnaround area. The drive wheels are based on size of the treads and drive chain and are, as an example, commonly of a 750 mm diameter for most escalator systems. Around each drive wheel a drive chain is guided and driven.
There also exist passenger conveyors in which propulsion of the drive chain(s) does not take place in the vicinity of the turnaround sections, but rather in, e.g., the midsections (load section or return section). In passenger conveyors of this type, a turnaround plate or an essentially semicircular guideway may be provided instead of the chain turnaround wheel such that the drive chain rollers follow a path defined by the turnaround plate or the guideway. The drive chain rollers are reversed from the load section into the return section of the passenger conveyor in the turnaround plate or the guideway. In this respect, the term turnaround section is intended to cover all types of constructions, e.g. chain turnaround wheels, turnaround guideways or turnaround plates.
The treads of a passenger conveyor, e.g an escalator or a moving walkway, typically comprise essentially box-shaped elements with a tread surface and a front side that is exposed in the inclined region of the escalator and referred to as the“riser.” In case of a moving walkway the riser is typically never exposed to the passenger. The remaining lateral, bottom and rear sides of the box, which also are never exposed to the passengers during operation of the escalator or moving walkway, may also be closed, but frequently remain open. This applies, in particular, to the underside of the tread which is situated opposite to the tread surface and to the rear side of the step. The side walls of the tread which are directed toward the drive chain are typically arranged regularly for structural reasons. In instances in which a rear wall of the box-like tread is not provided opposite to the front side, the side walls of the box which are directed toward the drive chains may have a triangular shape that is tapered toward the bottom, and the tread itself may have only a relatively small thickness in its rear region, by comparison to the thickness of the tread in the vicinity of the front side. The weight and the material requirement can be significantly reduced by these measures.
The treads are typically fastened to the drive chain(s) by means of a drive chain roller axle. The drive chain roller axle usually extends through the tread body and, in case of two drive chains arranged laterally, is connected to the drive chains at both of its free ends. The tread is customarily manufactured from a material that exhibits the required strength for carrying a passenger load and that can be easily processed, for example, a material that can be extruded such as aluminum, an aluminum alloy, or a plastic. The drive chain roller axle is manufactured from a stronger material, for example, iron or steel.
In a state of the art passenger conveyor, the individual treads typically move in a “channel” that is laterally limited by panel elements or “skirt boards.” These skirt boards are rigidly arranged to the frame of the passenger conveyor, with the treads moving relative to these (stationary) skirt boards. The gap formed between the (moving) treads and the (stationary) skirt boards needs to be kept very small for safety reasons, so as to reliably ensure that no objects or clothing of passengers are pulled into this gap and become trapped therein.
The requirement to ensure a very narrow gap is associated with a high maintenance expenditure. In certain instances, it is entirely impossible to fulfill the safety requirements with respect to a narrow gap. One option for lowering this risk potential, other than with a narrow gap, consists of providing a bottom panel that is fixedly mounted to the treads and thereby moves together with the treads. Such a movable bottom panel is, e.g., described in U.S. Pat. No. 4,470,497. Such bottom panels according to the prior art have either the disadvantage that they project relatively far upward beyond the tread surface of the tread in the horizontal regions of an escalator, e.g., at the entry point and the exit point, or that they have a relatively complicated design.
DE 23 46 266 A1 discloses another approach using pivotable lateral skirt panels. Here, each step of the escalator has mounted thereto a pair of lateral skirt panels. The skirt panels are supported by the step chain roller axles by which the respective step and the steps adjacent to it are connected to the step chain. Thereby, the lateral skirt panels perform a pivot movement with respect to the respective tread surface corresponding to the rising/lowering of the step riser, as the steps travel in the inclined/horizontal sections of the endless travel path. This construction, however, requires that both the lateral skirt panels and the step chain links have the same length as the tread surfaces of the steps, and in consequence leads to large bending radii in the turnaround sections.
U.S. Pat. No. 6,450,316 B1 discloses an escalator having a construction of lateral panels formed by a combination of circular bottom panels fixedly mounted to the tread surface of each step, and movable bridge parts positioned in between two consecutive of the circular bottom panels. The movable bridge parts are associated with a corresponding link of the step chain and remain stationary thereto, as the step chain travels through different sections of the endless travel path. Each of the bridge parts has two concave interface edge portions that cooperate with the circular edge portions of adjacent bottom panels, such as to cooperate to provide a continuous barrier along each lateral side of the steps along the escalator travel path. Also this construction requires an allocation of exactly one circular bottom panel and one bridge portion at each lateral side to each step, and in consequence, similar to DE 23 46 266 A1, leads to large bending radii in the turnaround sections.
It would be beneficial to have available an alternative construction of lateral panel members providing for sufficient closure of a gap formed at lateral sides of the transporting elements of a passenger conveyor, which construction needs less space, particularly in the turnaround sections of the tread band, and is efficient to realize.